1. Field of the Invention
The present invention relates to a pressure-sensitive adhesive for applying an optically functional film, an optically functional film and a production process for the same.
2. Description of the Related Art
Liquid crystal display panels have become rapidly widespread as a display device in place of CRT, and demands therefor are expanding. A liquid crystal display panel has the advantage that it is thin and has low power consumption. On the other hand, it has the defect that it is unsatisfactory in terms of a luminance and a viewing angle as compared with CRT. Accordingly, it has been tried to solve the above defect by using a backlight and scattering light transmitting a panel.
A method in which a light-diffusing pressure-sensitive adhesive layer comprising inorganic fine particles dispersed in a transparent resin is provided in a liquid crystal cell to thereby enhance expansion of a viewing angle and a displayed quality is proposed as one of the above trials (refer to a patent document 1 and claims thereof). Further, in a reflection type liquid crystal display, proposed is a liquid crystal display in which a diffusing pressure-sensitive adhesive layer comprising a pressure-sensitive adhesive blended with a filler for diffusing light is applied on a liquid crystal panel in order to diffuse light transmitted, and it is disclosed to provide a release sheet on both sides of the diffusing pressure-sensitive adhesive layer (refer to a patent document 2 and claims thereof).
However, though the above liquid crystal display panels are inhibited from causing an uneven luminance by diffusion of light and have even brightness, they used to have the problem that they are inferior in durability. To be specific, bubbles are produced in a light-diffusing pressure-sensitive adhesive layer with the passage of time in using a liquid crystal display panel to cause an uneven luminance. Further, lifting and peeling brought about with the passage of time in a polarizing plate disposed on a liquid crystal cell via a pressure-sensitive adhesive or a retardation film disposed between a polarizing plate and a liquid crystal cell via a pressure-sensitive adhesive in order to improve the viewing angle characteristics are caused in a certain case. Also, in the case of providing release sheets on both sides of a diffusing pressure-sensitive adhesive layer, the diffusing pressure-sensitive adhesive layer is peeled off (hereinafter “parting”) as well from the other release sheet when peeling one release sheet from the diffusing pressure-sensitive adhesive layer.    Patent document 1: Japanese Patent Application Laid-Open No. 133606/2001    Patent document 2: Japanese Patent Application Laid-Open No. 223712/1999